Due to recent changes in lifestyle, an increasing densification and air-tightness in residential environments, and the like, various bacteria and molds are becoming more widespread in human living spaces. Especially in an environment with high temperature and humidity like Japan, bacteria and molds proliferate easily on the surfaces of textile materials such as absorbent articles and other hygiene supplies, clothing, and the like. This can result in skin disorder, a loss of product quality due to fiber deterioration and discoloration, or an unpleasant odor that accompanies the proliferation of microbes. In particular, the development of an unpleasant odor is considered to be a problem, and demand has grown in recent years for both bacterial growth inhibition and unpleasant odor clearance. Typical odor-causing components include ammonia, trimethylamine and other basic gases; sulfur-containing compounds such as hydrogen sulfide, and methyl mercaptans; and short chain fatty acids such as acetic acid, butyric acid, valeric acid and caproic acid, produced by bacterial decomposition of secretions from the sweat glands, sebaceous glands, etc. Additionally, nitrogen-containing cyclic compounds such as indoles, skatoles, and the like are known as ingredients that can make people feel uncomfortable.
Typical methods for removing these odor-causing substances include physical adsorption methods wherein the odor is adsorbed by using a porous medium such as activated charcoal, silica gel, and the like; chemical methods wherein the odor-causing substance is reacted in a neutralizing or oxidation reaction and removed; and sensory methods wherein the uncomfortable feeling is suppressed by a strong fragrance, and the like.
On the other hand, the unpleasant odor accompanying the proliferation of microbes can be controlled indirectly by imparting antibacterial properties to fibers. Unpleasant odors can be efficiently removed and the generation thereof is controlled by using a combination of the odor-removing methods noted above. In addition to conventional means of adding an inorganic antibacterial and deodorizing agent containing silver, zinc, and the like to the fibers, for example, Japanese Patent Application Publication (hereunder referred to as “JP KOKAI”) No. 2000-303250 has proposed fibers with catechins, which are contained in a tea leaf extract and the like, added thereto, JP KOKAI No. 2003-253559 has proposed fibers with rosemary essential oil and the like added thereto.
Although antibacterial and deodorant fibers to which the aforementioned tea leaf extract and plant liquid extract are added have good antibacterial and deodorant properties, problems remain because these additives are easily oxidized by oxidants in the air such as nitrogen dioxide and other nitrogen compounds, resulting in discoloration including yellowing, reddening, and the like. Consequently, the antibacterial and deodorant properties are not only decreased thereby, but the use of such fibers in paper diapers, sanitary napkins, incontinence pads and other hygiene products has also been limited, mainly due to concerns about unacceptable appearance caused by discoloration.